This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 50 |
| 5 | 136 |
| 6 | 364 |
| 7 | 966 |
| 8 | 2550 |
| 9 | 6710 |
| 10 | 17622 |
| 11 | 46224 |
| 12 | 121160 |
| 13 | 317434 |
| 14 | 831430 |
| 15 | 2177322 |
| 16 | 5701290 |
| 17 | 14927768 |
| 18 | 39083988 |
| 19 | 102327390 |
| 20 | 267903350 |
| 21 | 701391022 |
| 22 | 1836283246 |
| 23 | 4807480608 |
| 24 | 12586194000 |
| 25 | 32951158706 |
| 26 | 86267374854 |
| 27 | 225851115906 |
| 28 | 591286215650 |
| 29 | 1548007923880 |